The efficiency of BCD devices could be improved if trench-based VDMOS (TB-VDMOS or TB-MOS) transistors could be added to existing integrated BCD process flows. Specifically, trench-based VDMOS transistors provide improved Ron scaling as compared to planar gate VDMOS or laterally diffused MOS (LDMOS) transistors. A mechanical switch's “on/off” state is determined by physically changing the switch's position. Transistor switches use an electrical input at the gate of the transistor to turn “on” or “off”. A positive voltage turns the switch on and a negative voltage turns it off. In design schematics, the “on” state is represented as a resistor and the “off” state as a capacitor. A low resistance allows more of the signal to travel from one port to another when the switch is on. This metric is called Ron. Ron is inversely proportional to the width of the conventional transistor. The wider the transistor is, the lower the resistance is, which allows more of the signal to get through.
Thus, the integration of trench-based VDMOS in BCD devices has great potential to improve high voltage (HV) device performance, through improved Ron. Further, trench-based VDMOS may provide enhanced device breakdown voltage (BV). However, methods to integrate trench-based VDMOS transistors in BCD devices include time intensive and difficult processing techniques and are not cost effective. For example, prior methods have used high energy implantation and diffusion process using phosphorous oxychloride (POCl3), as well as long duration drive-in processing to connect a buried drain layer to the device front side for drain connection, and long duration LOCOS oxidation processing to form breakdown voltage enhancement regions.
Accordingly, it is desirable to provide improved trench-based VDMOS transistors, such as trench-based VDMOS transistors in BCD devices. Further, it is desirable to provide a method for fabricating an integrated circuit including a trench-based VDMOS transistor that is cost effective and time efficient. Also, it is desirable to integrate trench-based VDMOS transistors in BCD device process flow. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.